The development of discrete track media (DTM), in which adjacent recording tracks are separated by a groove or nonmagnetic body in order to suppress magnetic interference between tracks, and bit patterned media (BPM), in which adjacent recording bits are separated by a groove or nonmagnetic body in order to suppress magnetic interference between bits, has allowed for the realization of high density recording, where these technologies aid in the control of magnetic interference between adjacent magnetic data storage areas (tracks or bits).
There has been strong demand in recent years for greater volume in magnetic recording devices and for higher recording density, not only in domestic electronic appliances such as personal computers, but also other devices equipped with compact, large-capacity magnetic disk(s). In order to respond to this demand, there has been great effort put into developing magnetic heads and magnetic recording media. An increased areal recording density is desired for these devices, and efforts are being made to reduce the scale and to achieve even more dramatic increases in recording density.
Surface planarity is important in magnetic recording media in order to maintain flying stability of the magnetic head. Surface planarity is especially important in the case of DTM and BPM in which the areal recording density is high and the recording domain is small, such that the grooves between magnetic regions are filled by nonmagnetic material. In addition, with DTM and BPM, a protective film made of a carbon-based material is generally formed on the recording layer in order to protect the recording layer and to absorb lubricant, in the same way as with conventional recording media. Among carbon-based materials that may be used for the nonmagnetic material, one preferred material is diamond-like-carbon (DLC), which is amorphous, and therefore has excellent surface planarity, durability, and corrosion resistance.
Meanwhile, improvements in the reliability of DTM and BPM have brought to light the problems of corrosion caused by damage when the magnetic film is rendered uneven through dry etching or the like, and corrosion caused by extremely small defects and gaps between the magnetic region and nonmagnetic region of the recording layer. One example of a conventional technology for improving corrosion resistance involves a soft magnetic underlayer which is the primary cause of corrosion in perpendicular magnetic recording media. The corrosion resistance is improved by selecting a particularly resistant combination of the structure and material of the seed layer, which is the layer above the soft magnetic underlayer. In addition, there is another conventional method to inhibit corrosion of the magnetic region in DTM and BPM by forming a conductive film between the recording layer and the protective film.
However, if a protective film is formed as the layer above the magnetic region in order to inhibit corrosion thereof, the magnetic distance between the magnetic head and the magnetic recording medium increases and the magnetic recording characteristics deteriorate. On the other hand, if the protective film is made thinner in order to improve the magnetic characteristics, it is difficult to achieve results which satisfy the product performance from the point of view of corrosion resistance. Accordingly, with conventional technologies of preventing corrosion of the magnetic region of the magnetic recording layer, there are problems, such as problems in achieving both high magnetic recording characteristics and corrosion resistance at the same time.